Ultrasonic probe and ultrasonic device

ABSTRACT

An ultrasound probe comprises therapeutic transducers which include a plurality of arrayed first transducer elements and emit therapeutic ultrasounds to a subject, and diagnostic transducers which include a plurality of arrayed second transducer elements and emit diagnostic ultrasounds to the subject and receive the diagnostic ultrasounds, wherein the therapeutic transducers are stacked over the diagnostic transducers.

TECHNICAL FIELD

The present invention relates to an ultrasound probe and an ultrasoundapparatus for use in ultrasound therapy.

BACKGROUND ART

In an ultrasound apparatus, therapeutic ultrasounds are emitted via adiagnostic probe kept in contact with the body surface of a subject, andultrasound images (e.g. tomograms and M-mode images) are reconstructedon the basis of reflected echo signals generated from the subject. Also,a target region is uninvasively treated by emitting therapeuticultrasounds onto the subject via a therapeutic probe.

In performing an ultrasound therapy, a diagnostic probe and atherapeutic probe are usually arranged alongside each other on the bodysurface of the subject in order to emit therapeutic ultrasounds whilechecking the target region by its ultrasound images (see, e.g., JapanesePatent Application Laid-Open No. 5-220152).

However, arranging a diagnostic probe and a therapeutic probe alongsideeach other on the body surface as in the conventional practice resultsin a difference in scanning coordinates between the diagnosticultrasounds and the therapeutic ultrasounds according to the differencebetween the contact positions of the two probes. Moreover, since thecontact positions of the two probes are determined by the operator asdesired, the difference in scanning coordinates is not constant.Therefore, while finding out the difference in scanning coordinatesbetween the two probes on every occasion of therapeutic action, thecoordinate position of the target region is determined on the basis ofultrasound images acquired with the diagnostic probe, the coordinateposition is converted into the coordinate system of the therapeuticprobe, and therapeutic ultrasounds are emitted onto the target regionaccordingly. As a result, particular care should be taken inmanipulating the therapeutic probe and the diagnostic probe, invitinginconvenience in the use of probes.

DISCLOSURE OF THE INVENTION

An object of the present invention is to realize an ultrasound probe andan ultrasound apparatus suitable for use in ultrasound therapy.

In order to solve the problem noted above, an ultrasound probepertaining to the invention comprises therapeutic transducers, includinga plurality of arrayed first transducer elements, for emittingtherapeutic ultrasounds to a subject; and diagnostic transducers,including a plurality of arrayed second transducer elements, foremitting diagnostic ultrasounds to the subject and receiving thediagnostic ultrasounds reflected by the subject, wherein the therapeutictransducers and the diagnostic transducers are stacked.

According to the invention, since it is possible to so position thescanning coordinates of therapeutic ultrasounds from the therapeutictransducers and those of diagnostic ultrasounds from the diagnostictransducers as to coincide with each other, the control accuracy of theposition of irradiation with the therapeutic ultrasounds can beenhanced. Also, e.g., the center of the aperture of the therapeutictransducers can be so positioned as to coincide with that of theaperture of the diagnostic transducers.

Further, an ultrasound apparatus pertaining to the invention comprisesthe aforementioned ultrasound probe; a therapeutic transmitting devicefor generating driving signals for the therapeutic transducers; adiagnostic transmitting device for generating driving signals for thediagnostic transducers; an image constructing device for reconstructingultrasound images on the basis of reflected echo signals received by thediagnostic transducers; and a detecting means for detecting the state ofthe therapy of the subject with the therapeutic ultrasounds, wherein thetherapeutic transmitting device has a warning function to output warninginformation on the basis of the state of the therapy detected by thedetecting means.

According to the invention, since it is possible to detect the progressof therapy with therapeutic ultrasounds, the operator is enabled to stopthe ultrasound therapy by an alarm sounded or a warning messagedisplayed, resulting in increased operating ease of the ultrasoundapparatus. Also, the target region can be prevented from beingexcessively irradiated with therapeutic ultrasounds.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configurative diagram of an ultrasound apparatus of a firstembodiment according to the present invention;

FIG. 2 is a perspective view schematically showing the ultrasound probeof the first embodiment according to the invention;

FIG. 3 is a sectional view along line III-III in FIG. 2;

FIG. 4 is a perspective view schematically showing an ultrasound probeof another embodiment;

FIG. 5 is a time chart illustrating the operation of the ultrasoundprobe;

FIG. 6 is a configurative diagram of an ultrasound apparatus of a secondembodiment according to the invention;

FIG. 7 is a configurative diagram of an ultrasound apparatus of a thirdembodiment according to the invention;

FIG. 8 is a configurative diagram of an ultrasound apparatus of a fourthembodiment according to the invention;

FIG. 9 is a perspective view schematically showing an ultrasound probeof a fifth embodiment according to the invention;

FIG. 10 is a perspective view schematically showing another example ofan ultrasound probe of the fifth embodiment according to the invention;

FIG. 11 is a perspective view schematically showing still anotherexample of an ultrasound probe of the fifth embodiment according to theinvention;

FIG. 12 is a configurative diagram of a therapeutic ultrasoundtransmitting unit of a seventh embodiment according to the invention;and

FIG. 13 is a diagram for describing the principle of avoidinginterference between the incident wave and the reflected wave in aneighth embodiment according to the invention.

BEST MODES FOR CARRYING OUT THE INVENTION

A first embodiment to which an ultrasound probe and ultrasound apparatusaccording to the present invention are applied will be described. Thisembodiment is one example of an ultrasound probe in which a plurality ofdiagnostic transducers are stacked over the ultrasound emitting faces oftherapeutic transducers.

As shown in FIG. 1, an ultrasound apparatus 1 is configured of adiagnostic ultrasound unit 9, a therapeutic ultrasound transmitting unit24, a display device 18, an input device 20, a control device 21 and soforth. The diagnostic ultrasound unit 9 is provided with a diagnostictransmitting/receiving device 12 having a diagnostic transmittingdevice, an image composing device including a tomogram forming device 14and a blood stream image forming device 16, and so forth. Thetherapeutic ultrasound transmitting unit 24 is provided with atherapeutic transmitting device 25, an alarming device 27 and so forth.And the diagnostic transmitting/receiving device 12 and the therapeutictransmitting device 25 are connected to an ultrasound probe 10.

The diagnostic transmitting/receiving device 12 generates drivingsignals for transmitting diagnostic ultrasounds to the ultrasound probe10, and receives reflected echo signals outputted from the ultrasoundprobe 10. The tomogram forming device 14 reconstructs tomograms on thebasis of the reflected echo signals. The blood stream image formingdevice 16 figures out the blood stream velocity from the Doppler shiftof reflected echo signals and reconstructs blood stream images on thatbasis.

The therapeutic transmitting device 25 generates driving signals foremitting therapeutic ultrasounds to the ultrasound probe 10. Thealarming device 27 has a warning function of sounding a buzz ordisplaying a warning message at an input instruction. The display device18 displays tomograms and blood stream images on the display screen of amonitor. The input device 20 is formed to have a keyboard and a pointingdevice, such as a mouse.

The ultrasound probe 10 emits ultrasounds for diagnostic and therapeuticpurposes, and is contained in a headset 11. The headset 11 comprises theultrasound probe 10 and a probe cooling device including water bags 32 aand 32 b, a circulation path 36 and a radiator device 34. The water bags32 a and 32 b are formed in a bag shape, holding a coolant (e.g. water)within. Incidentally, the water bags 32 a and 32 b need not bebag-shaped. The circulation path 36 guides water in the water bags 32 aand 32 b to the radiator device 34. The radiator device 34 radiates theheat of the guided water into the external atmosphere.

Detailed configuration of the ultrasound apparatus 1 composed in thisway will be described together with its operations. First, the headset11 is put on the head of the subject. This causes the water bags 32 aand 32 b of the headset 11 to be fixed in a state of being in contactwith the outer skin (e.g. near the temples) of the subject's head. Andthe ultrasound probe 10 is brought into contact with the rear face ofthe water bag 32 a.

Then, driving signals are supplied to the ultrasound probe 10 from thediagnostic transmitting/receiving device 12. The supplied drivingsignals cause diagnostic ultrasounds to be emitted towards the subjectfrom the ultrasound probe 10. The emitted diagnostic ultrasounds arereflected or scattered by living tissues or the blood stream within thehead. Those diagnostic ultrasounds are received by the ultrasound probe10 as reflected echo signals. The received reflected echo signals arereconstructed into tomograms by the tomogram forming device 14. Thereconstructed tomograms are displayed on the monitor of the displaydevice 18. By observing the displayed tomograms, the position of thetarget region (e.g. cerebral thrombosis) can be accurately identified.

And the input of the position of the target region (e.g. cerebralthrombosis) in the tomograms is set from the input device 20. On thebasis of the positional coordinates of the cerebral thrombosis so set,driving signals are generated by the therapeutic transmitting device 25.The generated driving signals are supplied to the therapeutictransmitting device 25 of the ultrasound probe 10. This enables thecerebral thrombosis to be irradiated with therapeutic ultrasounds fromthe ultrasound probe 10 to dissolve the cerebral thrombosisuninvasively.

When the cerebral thrombosis is dissolved, the blood vessel is reopenedto let the blood flow. The blood which has begun to flow causesdiagnostic ultrasounds to be reflected or scattered as reflected echosignals. The Doppler shift of those reflected echo signals is figuredout by the blood stream image forming device. On the basis of theDoppler shift so figured out, blood stream images (e.g. two-dimensionalDoppler blood stream images or pulse Doppler FFT measured images) arereconstructed and displayed.

In such an ultrasound apparatus, if the diagnostic probe and thetherapeutic probe were separate, the two probes would have to bearranged alongside each other and brought into contact with the waterbag 32 a. In this case, as differences in scanning coordinates wouldoccur between diagnostic ultrasounds and therapeutic ultrasoundsaccording to the difference between the two probes in contact position,care should be taken of the manipulation of the therapeutic probe andthe diagnostic probe in performing ultrasound therapy. Unlike that, inthe present embodiment, the target region can be precisely irradiatedwith therapeutic ultrasounds by using an ultrasound probe integrallyformed by stacking diagnostic transducers and therapeutic transducers.

Next, the ultrasound probe 10 will be described in detail. As shown inFIG. 2, the ultrasound probe 10 is composed by stacking diagnostictransducers 52, therapeutic transducers 50, a backing material 54 and acooling device 56 in this order from the subject side. The therapeutictransducers 50 generate ultrasounds of a relatively low frequency (e.g.about 500 kHz) while the diagnostic transducers 52 generate ultrasoundsof a relatively high frequency (e.g. about 2 MHz). Therefore, as theultrasounds generated by the diagnostic transducers 52 are moredifficult to be transmitted by an obstacle than the ultrasoundsgenerated by the therapeutic transducers 50 are, the diagnostictransducers 52 are stacked over the therapeutic transducers 50 so thatthe former can be closer to the subject.

The therapeutic transducers 50 are formed by arraying a plurality oftransducer elements 50 a through 50 d. The therapeutic transducerelements 50 a through 50 d, each formed of a piezoelectric ceramiccuboid, are arrayed at equal intervals with the longitudinal directionsof ultrasound emitting faces 51 being parallel to one another. Thearrayed therapeutic transducer elements 50 a through 50 d convert thedriving signals from the therapeutic ultrasound transmitting unit 24into mechanical transducers, and deflect them to emit therapeuticultrasounds to the target region (e.g. cerebral thrombosis).

The diagnostic transducers 52 are formed by arraying a plurality oftransducer elements 52 a through 52 p. The diagnostic transducerelements 52 a through 52 p, each formed of a piezoelectric ceramiccuboid, are made smaller than the transducer elements 50 a through 50 dof the therapeutic transducers 50 in order to enhance the resolution ofthe tomograms to be reconstructed. And more than one of diagnostictransducer elements 52 a through 52 p are distributed over theultrasound emitting faces 51. For example, as shown in FIG. 2, thediagnostic transducer elements 52 a through 52 d are distributed overthe ultrasound emitting face 51 of the therapeutic transducer element 50a. Thus, the reverse faces of the diagnostic transducer elements 52 athrough 52 d to an ultrasound emitting face 53 are joined to theultrasound emitting faces 51 of the therapeutic transducer element 50 a.And the diagnostic transducer elements 52 a through 52 d are arranged atequal intervals in the shorter side direction of the ultrasound emittingface 51 and in parallel to the longitudinal direction of the ultrasoundemitting face 53. The same is true of the diagnostic transducer elements52 e through 52 p. Each of the arrayed diagnostic transducer elements 52a through 52 p converts electric signals, e.g. in a pulse form, from thetransmitting/receiving device 12 into mechanical transducers, deflectsthem to transmit diagnostic ultrasounds to the subject, and at the sametime receives reflected echo signals generated from the subject andconverts them into electric signal pulses.

The backing material 54 is formed of, among other things, alow-impedance layer having a thickness of half the wavelength of thetherapeutic ultrasounds, and disposed superposing over the reverse facesof the therapeutic transducer elements 50 a through 50 d to theultrasound emitting faces 51. This causes ultrasounds to be transmittedto the side reverse to the emitting direction, out of the ultrasoundsemitted from the therapeutic transducers 50, to be reflected by thebacking material 54 and proceed towards the subject. Therefore, it ispossible to efficiently emit therapeutic ultrasounds towards thesubject.

Further, the cooling device 56 is disposed superposing over the reverseface of the backing material 54, i.e. the face reverse to the ultrasoundemitting direction of the therapeutic transducers 50. The cooling device56, formed of a Peltier element or the like, absorbs heat by the Peltiereffect when a current is let flow through it, and radiates the heat intothe external atmosphere. It can thereby restrain the temperature rise ofthe ultrasound probe 10.

One example of dimensions of such an ultrasound probe 10 will bedescribed with reference to FIG. 3. The thickness t₁ of the therapeutictransducer elements 50 a through 50 d, the thickness t₂ of thediagnostic transducer elements 52 a through 52 p, the array pitch p₁ ofthe therapeutic transducer elements 50 a through 50 d and the arraypitch p₂ of the diagnostic transducer elements 52 a through 52 p shownin FIG. 3 are set to be close to the respective values calculated by thefollowing equations (1) through (4):

$\begin{matrix}{t_{1} = {\frac{\lambda_{1}}{2} = \frac{c}{2f_{1}}}} & (1) \\{t_{2} = {\frac{\lambda_{2}}{2} = \frac{c}{2f_{2}}}} & (2) \\{p_{1} = \frac{cw}{2f_{1}}} & (3) \\{p_{2} = \frac{cw}{2f_{2}}} & (4)\end{matrix}$Here, f₁ is the frequency of the therapeutic ultrasounds emitted fromthe therapeutic transducers 50; λ₁, the wavelength of the therapeuticultrasounds; f₂, the frequency of the diagnostic ultrasounds emittedfrom the diagnostic transducers 52; λ₂, the wavelength of the diagnosticultrasounds; c, the longitudinal wave sound velocity of the therapeutictransducers 50 in the thickness direction, i.e. the ultrasound emittingdirection; and cw, the sound velocity in water or in a living body.

In this embodiment, the frequency f₁ is supposed to be 500 kHz and thefrequency f₂, 2 MHz. Therefore, if the sound velocity c is 3.3 mm/μs andthe sound velocity cw, 1.538 mm/μs, the thickness t₁ will be 3.3 mm, thethickness t₂, 0.83 mm, the array pitch p₁, 1.54 mm and the array pitchp₂, 0.39 mm according to equations (1) through (4). Further, supposingthat the number of the diagnostic transducers is 64, the array size,i.e. the ultrasound aperture D, of the ultrasound probe 10 shown in FIG.3 will be D=64×p₂=24.6 mm. If the dimensions are such as stated above,even if, for example, the opening where the skull is thin and permitsrelatively ready transmission of ultrasounds (e.g. near the temples) islimited to 30 mm square for example, the ultrasound aperture D of theultrasound probe 10 can be accommodated within that range. Therefore,the losses of the diagnostic ultrasounds and of the therapeuticultrasounds due to the thickness of the skull can be reduced.

Although the number of the diagnostic transducers is supposed to be 64and the ultrasound aperture D=64×p₂=24.6 mm in the case described above,the number N of the diagnostic transducers may be any desired naturalnumber; it is possible to enlarge the ultrasound aperture D=N×p₂ byincreasing the number N of the diagnostic transducers or, conversely, tonarrow the ultrasound aperture D by reducing the number N of thediagnostic transducers.

Further, in order to improve the acoustic effect, the distances d₁between the therapeutic transducer elements and the distances d₂ betweenthe diagnostic transducer elements should be as narrow as practicable.

The frequencies of the ultrasounds to be used are determined from theviewpoints of effectiveness and safety. For example, where the limitvalue of the ultrasound intensity of the therapeutic ultrasounds is 720mW/cm, in order to keep the temperature of the living tissue at 2° C. orless, the frequency f₁ is kept at 580 kHz or less. This makes itpossible to keep the thermal index (TI), the indicator of the intensityof the thermal action of ultrasounds, at no more than 2. Further, thefrequency f₁ is adjusted to 390 kHz or above. This makes it possible tokeep the mechanical index (MI), the indicator of the intensity of themechanical action of ultrasounds to destroy tissue cells by cavitationsor the like arising within the blood vessel, at 0.25 or below.

With respect to the embodiment shown in FIGS. 2 and 3, an ultrasoundprobe 10 having four therapeutic transducer elements 50 a through 50 dand sixteen diagnostic transducer elements 52 a through 52 p wasdescribed, but the number of transducer elements of each type can bealtered as appropriate. As shown in FIGS. 2 and 3, if the ratio betweenthe array pitch of therapeutic transducer elements and the array pitchof diagnostic transducer elements is integral, the phase control systemand the circuit form can be simplified.

In the embodiment shown in FIG. 4, four therapeutic transducer elementsand fifteen diagnostic transducer elements are disposed, soundinsulators 53 are provided to fill the gaps between the therapeutictransducer elements and constitute the base of the diagnostic transducerelements. Examples of material for the sound insulators 53 includeparticulates of tungsten or the like and micro-balloons dispersed inepoxy resin. If the configuration is such that the ratio between thearray pitch of therapeutic transducer elements and the array pitch ofdiagnostic transducer elements is not integral as shown in FIG. 4, anarrangement in which the gratings of the two types of transducerelements do not degenerate can be realized, and control can be soperformed as not to let the grating lobes overlap each other.

Next will be described the operations of the ultrasound probe 10 withreference to FIG. 5. Usually, when the therapeutic transducers 50 andthe diagnostic transducers 52 are driven at the same time, therapeuticultrasounds from the therapeutic transducers 50 are received by thediagnostic transducers 52 as noise. Therefore in this embodiment, asshown in FIG. 5, a therapeutic ultrasound beam (T beam) and a diagnosticultrasounds beam (D beam) are alternately emitted, each at a set pointof time. Incidentally, the emission timings of the T beam and the D beammay be altered as appropriate to prevent noise generation.

First, the D beam (e.g. 2 MHz in frequency) is emitted from thediagnostic transducers 52 for 0.2 second for example. After the emissionof the D beam, the T beam (e.g. 500 kHz in frequency) is emitted fromtherapeutic transducers 50 for 3 seconds for example. Repetition of suchactions causes the D beam to form a tomogram and a two-dimensional bloodstream image and the T beam to treat the target region. Incidentally,since it is sufficient for the duration of D beam emission to be longenough to form a tomogram or a two-dimensional blood stream image, theduration is set, for example, in a range of 0.01 to 0.2 second. Theduration of T beam emission is set, for example, between 1 and 10seconds as appropriate. To add, in order to improve the resolution oftomograms, the D beam is formed by transmitting at set intervals a burstwave consisting of pulse waveforms put together over ½ to 20wavelengths, for example. The T beam is formed by transmittingconsecutively transmitted ultrasounds so that a prescribed mechanicalindex can be secured.

In this embodiment, since the scanning coordinates of the T beam fromthe therapeutic transducers 50 and those of the D beam from thediagnostic transducers 52 can be so positioned as to coincide with eachother, the position of irradiation with therapeutic ultrasounds can bemore accurately controlled. Therefore, the target region whose positionhas been identified with the D beam can be accurately irradiated withthe T beam.

Further, as it is possible to bring the center of the aperture of thetherapeutic transducers 50 into coincidence with the center of theaperture of the diagnostic transducers 52, there is no particular needfor coordinate conversion, and accordingly the control mechanism can besimplified.

Moreover, by electrically controlling the ultrasound probe 10 withouthaving to move it along the body surface, tomograms are reconstructed byusing the D beam and the target region can be treated by using the Tbeam. Therefore, the length of time required for treatment can beshortened, and the efficiency of ultrasound therapy can be enhanced inother ways as well. For example, whereas any cerebral thrombosis shouldbe dissolved in a short period from the time when a cerebral infarctionhas occurred, the cerebral thrombosis can be dissolved promptly andaccurately in this embodiment.

A second embodiment to which an ultrasound probe and an ultrasoundapparatus according to the invention are applied will be described withreference to FIG. 6. This embodiment differs from the first embodimentin that, when a thrombosis has been dissolved and blood begins to flow,therapeutic ultrasounds are stopped or the amplitude of therapeuticultrasounds is narrowed. FIG. 6 shows a configurative diagram of anultrasound apparatus of this embodiment.

Usually, when any thrombosis has been dissolved with therapeuticultrasounds, irradiation with therapeutic ultrasounds may be continuedeven after the thrombosis has been dissolved and blood begins to flow.In view of this possibility, a blood stream detecting device 22 isprovided in this embodiment as shown in FIG. 6. The blood streamdetecting device 22, which detects the intensity of the Doppler shiftsignal of reflected echo signals generated from the treated region,namely the blood stream velocity, outputs a control instruction to thetherapeutic ultrasound transmitting unit 24 when the detected bloodstream velocity is above a setpoint (α).

If, for example, it is determined that the blood stream velocitydetected by the blood stream detecting device 22 is not above thesetpoint (α), no control instruction is outputted to the therapeuticultrasound transmitting unit 24. Therefore, the therapeutic transmittingdevice 25 maintains or increases the energy (e.g. amplitude orfrequency) of therapeutic ultrasounds. Or if it is determined that thedetected blood stream velocity is above the setpoint, a controlinstruction will be outputted to the therapeutic ultrasound transmittingunit 24, and the therapeutic transmitting device 25 will either reducethe energy or totally stop the emission of therapeutic ultrasounds.Then, the alarming device 27 issues a warning sound (e.g. buzz or voice)or displays a warning message on the display device 18.

In this embodiment, it is possible to detect dissolution of thethrombosis and the start of blood flowing. This enables the amplitude orfrequency of therapeutic ultrasounds to be reduced or their emission tobe stopped automatically when blood begins to flow. Therefore, thetreated region can be prevented from excessively irradiated withtherapeutic ultrasounds.

Incidentally, it is also conceivable to stop therapeutic ultrasoundsmanually when a warning sound or a warning message is issued. Althoughthis embodiment has been described with the use of the ultrasound probe10 of the first embodiment, the ultrasound apparatus of this embodimentcan also be applied where the diagnostic probe and the therapeutic probeare separated from each other.

A third embodiment to which an ultrasound probe and an ultrasoundapparatus according to the invention are applied will be described withreference to FIG. 7. This embodiment differs from the first embodimentin that, when the temperature of the ultrasound probe has risen abovethe set level, the frequency or amplitude of therapeutic ultrasounds isreduced or their emission is stopped. FIG. 7 shows a configurativediagram of an ultrasound apparatus in this embodiment.

Usually, when therapeutic and diagnostic ultrasounds are emitted fromthe ultrasound probe 10, part of the energy of the emitted ultrasoundsis converted into thermal energy within the ultrasound probe 10.Therefore the temperature of the ultrasound probe 10 may rise. In viewof this possibility, a temperature detecting device 28 is provided inthis embodiment as shown in FIG. 7. The temperature detecting device 28,intended to detect the temperature of the ultrasound probe 10, outputs acontrol instruction to the therapeutic ultrasound transmitting unit 24when the detected temperature exceeds a setpoint.

If, for example, it is determined that the temperature rise detected bythe temperature detecting device 28 does not exceed a setpoint (e.g. 2°C.), no control instruction is outputted to the therapeutic ultrasoundtransmitting unit 24. Therefore, the therapeutic transmitting device 25maintains or increases the energy (e.g. amplitude or frequency) oftherapeutic ultrasounds. Or if it is determined that the detectedtemperature rise exceeds the setpoint, a control instruction will beoutputted to the therapeutic ultrasound transmitting unit 24, and thetherapeutic transmitting device 25 will either reduce the energy ortotally stop the emission of therapeutic ultrasounds. Then, the alarmingdevice 27 issues a warning sound (e.g. buzz or voice) or displays awarning message on the display device 18.

In this embodiment, since it is possible to automatically restrain thetemperature rise of the ultrasound probe 10, the temperature rise can beprevented from inviting any side effect on the living tissue.Incidentally, instead of detecting the temperature of the ultrasoundprobe 10, the temperature of the water bag 32 a shown in FIG. 1 can bedetected. In short, the point is to detect a temperature correlated tothe therapeutic transducers 50 or the diagnostic transducers 52.

Incidentally, it is also conceivable to stop therapeutic ultrasoundsmanually when a warning sound or a warning message is issued. Althoughthis embodiment has been described with the use of the ultrasound probe10 of the first embodiment, the ultrasound apparatus of this embodimentcan also be applied where the diagnostic probe and the therapeutic probeare separated from each other.

A fourth embodiment to which an ultrasound probe and an ultrasoundapparatus according to the invention are applied will be described withreference to FIG. 8. This embodiment differs from the second embodimentin that, when the infarcted region is treated, a thrombolytic agent isused in combination, and the dose of thrombolytic agent is reduced or,its administration is stopped, when the thrombosis has dissolved. FIG. 8shows a configurative diagram of an ultrasound apparatus in thisembodiment.

Usually, when treating a thrombosis in an infarcted region, thethrombosis is irradiated with therapeutic ultrasounds, while athrombolytic agent is injected into the subject to accelerate thedissolution of the thrombosis. In that case, the thrombolytic agent maycontinue to be injected into the subject even after the thrombosis hasbeen dissolved and blood begins to flow.

In view of this possibility, a solvent injection control unit 30 isprovided in this embodiment as shown in FIG. 8. The solvent injectioncontrol unit 30 has an injection control device 31, an arithmeticprocessing device 29, an alarming device 33 and so forth. The injectioncontrol device 31 controls the dose of the thrombolytic agent injectedinto the subject via an injector probe 26. The arithmetic processingdevice 29 computes the dose of the thrombolytic agent to be injectedinto the subject on the basis of a control instruction from the bloodstream detecting device 22. The alarming device 33 sounds a warningbuzzer or displays a warning message on the basis of a controlinstruction from the blood stream detecting device 22.

If, for example, it is determined that the blood stream velocitydetected by the blood stream detecting device 22 does not exceed asetpoint (α), no control instruction will be issued to the solventinjection control unit 30. Therefore, the injection control device 31maintains or increases the dose of the thrombolytic agent. Or if it isdetermined that the detected blood stream velocity exceeds the setpoint(α), a control instruction will be issued to the solvent injectioncontrol unit 30, and the injection control device 31 will decrease theinjected dose or stop the injection of the thrombolytic agent on thebasis of the dose computed by the arithmetic processing device 29.Further, the alarming device 33 issues a buzz or voice or displays awarning message on the monitor 18.

This embodiment enables the injected dose of the thrombolytic agent tobe reduced or their emission to be stopped automatically when thethrombosis has been dissolved and blood begins to flow. Therefore, theliving tissue can be prevented from suffering a side effect due to anexcessive dose of the thrombolytic agent.

Incidentally, it is also conceivable to manually stop injecting thethrombolytic agent when a warning sound or a warning message is issued.Also, the injected dose of the thrombolytic agent may be displayed onthe display screen of the monitor 18 on a real time basis. This wouldenable the operator to objectively keep track of the injected dose ofthe thrombolytic agent.

Although this embodiment has been described with the use of theultrasound probe 10 of the first embodiment, the ultrasound apparatus ofthis embodiment can also be applied where the diagnostic probe and thetherapeutic probe are separated from each other.

A fifth embodiment to which an ultrasound probe and an ultrasoundapparatus according to the invention are applied will be described withreference to FIGS. 9 through 11. This embodiment differs from the firstembodiment in that the installation of the cooling devices is positionedon sides of the therapeutic transducers and the diagnostic transducers.FIG. 9 shows the ultrasound probe in this embodiment.

As shown in FIG. 9, cooling devices 56 a and 56 b are disposed on twosides of the therapeutic transducers 50 and the diagnostic transducers52. In this embodiment, the heat of the ultrasound probe 10 can beradiated into the external atmosphere by appropriately letting a currentflow through the cooling devices 56 a and 56 b. Therefore, it is madepossible to continuously irradiate the target region with ultrasoundsfor a relatively long time while keeping the temperature rise of theultrasound probe 10 at or below a setpoint (e.g. 2° C.). As a result,the length of time required for therapy can be shortened, and theefficiency of treatment can be enhanced in other ways as well.

Further with respect to the cooling devices 56, they can be installed inany positions if only they can cool the therapeutic transducers 50 orthe diagnostic transducers 52. For example, as shown in FIG. 10, acooling device 56 c can be so disposed as to cover sidewalls surroundingthe ultrasound probe 10.

It is also possible to use a metallic foil in addition to the coolingdevices. For example, as shown in FIG. 11, a metallic foil 60 isarranged over the ultrasound emitting faces of the diagnostictransducers 52 of FIG. 9. The metallic foil 60 so arranged is in contactwith the cooling devices 56 a and 56 b. This enables the heat generatedby the diagnostic transducers 52 to be absorbed by the metallic foil 60.The absorbed heat is guided to the cooling devices 56 a and 56 b via themetallic foil 60. The guided heat is radiated by the Peltier effect ofthe cooling devices 56 a and 56 b. Therefore, the temperature rise ofthe ultrasound probe 10 can be restrained. To add, the metallic foil 60is a conductor (e.g. metal) thinned to a few μm, formed of a materialwhich would not affect emission of ultrasounds.

Further, since the ultrasound emitting faces of the diagnostictransducers 52 are covered by the metallic foil 60, when the ultrasoundprobe 10 is brought into contact with the body surface, the temperatureof the ultrasound probe 10 is not directly transmitted to the subject.Therefore, the temperature of the ultrasound probe 10 can be preventedfrom causing a side effect to the subject.

A sixth embodiment to which an ultrasound probe and an ultrasoundapparatus according to the invention are applied will be described. Thisembodiment differs from the first through fifth embodiments in thattherapeutic ultrasounds in a burst wave form are emitted to avoidoccurrence of any side effect on the living tissue.

For example, where a cerebral infarction is to be treated, therapeuticultrasounds brought incident into the brain from the ultrasound probe 10may be reflected back by the inner wall of the skull in their proceedingdirection. This would occur because the skull is higher in acousticimpedance than the living tissues within the brain. The superposing ofreflected therapeutic ultrasounds (hereinafter referred to as reflectedwaves) over the therapeutic ultrasounds (hereinafter referred to asincident waves) brought incident into the brain from the ultrasoundprobe 10 and their mutual interference may give rise to standing waveswithin the brain. If the standing waves have a relatively high strength(amplitude) locally, they may bring on a side effect on the livingtissues within the brain.

In view of this possibility, the therapeutic transmitting device 25generates driving signals of a burst wave from the basic waveform inthis embodiment. As the driving signals so generated are supplied to thetherapeutic transducers 50, the burst wave is emitted from thetherapeutic transducers 50 to the subject. The duration of the burstwave then is set to be relatively short (i.e. 10 μs), and the restduration, relatively long (e.g. 100 μs to 300 μs). To add, a burst waveconsisting of pulse waveforms put together in which, for example, theduration of one wavelength is 2 μs is emitted.

For example, where it takes the reflected waves 100 μs of time to returnwithin the brain, the rest duration of the burst wave is set longer than100 μs. Incidentally, the emitting duration and the rest duration of theburst wave, which are altered as appropriate, are set in advance fromthe input device 20.

In this embodiment, after an incident burst wave T_(n) is reflectedback, the next burst wave T_(n+1) is brought to incidence. Therefore,the burst waves T_(n) and T_(n+1) do not overlap each other, so that anyside effect on the living tissue can be avoided.

Therapeutic ultrasounds, in particular, are less susceptible toattenuation when proceeding within the brain, because their frequencyis, for example, 500 kHz. Since the intensity of the reflected wave andthat of the incident wave are approximately equal for this reason, theintensity of the interfering wave is relatively high. In this respect,this embodiment enables interference between the reflected wave and theincident wave of therapeutic ultrasounds to be averted.

Diagnostic ultrasounds, since their frequency is usually set to, forexample, 2 MHz or above, are more susceptible to attenuation whenproceeding within the brain. Therefore, the intensity of the interferingwave is relatively low and, as in the case of diagnostic ultrasounds,the rest duration of the pulse wave or the burst wave may be setrelatively long.

Although the duration of burst wave emission is supposed to be 10 μs forexample, it may be altered as appropriate. The point is that, theduration may be of any length only if, even when the incident wave andthe reflected wave interfere with each other, it is made possible tokeep the duration of the interfering wave short to avoid its side effecton the living tissue.

Although this embodiment has been described with the use of theultrasound probe 10 of the first embodiment, the ultrasound apparatus ofthis embodiment can also be applied where the diagnostic probe and thetherapeutic probe are separated from each other.

A seventh embodiment to which an ultrasound probe and an ultrasoundapparatus according to the invention are applied will be described withreference to FIG. 12. This embodiment differs from the sixth embodimentin that the frequency of therapeutic ultrasounds is gradually raisedwith the lapse of emission time. FIG. 12 shows a configurative diagramof the therapeutic transmitting device 25 of FIG. 1.

As shown in FIG. 12, the therapeutic ultrasound transmitting device 24comprises a clock generator 70, a modulating signal generator 72, phaseshifter circuits 74 a through 74 m (m: a natural number), amplifiers(hereinafter referred to as amplifiers 76 a through 76 m). Incidentally,the phase shifter circuits 74 a through 74 m can be formed of delaycircuits. Sign m matches the number of therapeutic transducer elements50 a through 50 m constituting the ultrasound probe 10.

First, the basic waveform of a continuous wave is generated by the clockgenerator 70. The generated basic waveform is shifted in phase by thephase shifter circuits 74 a through 74 m. And each shifted basicwaveform, after being amplified by the amplifiers 76 a through 76 m, isinputted to the therapeutic transducers 50 as a driving signal. Theinputted driving signals cause the therapeutic transducers 50 to emittherapeutic ultrasounds. With the lapse of the emission time, themodulating signal generator 72 generates modulating signals. Thegenerated modulating signals are inputted to the phase shifter circuits74 a through 74 m. With the inputted modulating signals, the phaseshifter circuits 74 a through 74 m significantly modulate thefrequencies of the basic waveforms. The modulated waveforms are inputtedto the therapeutic transducers 50 as driving signals. This causestherapeutic ultrasounds whose frequencies are significantly modulated tobe emitted from the therapeutic transducers 50. For example, thefrequency of the ultrasounds at the starting time of emission (T=0)being represented by f₀ and their wavelength by λ₀, modulating signalsare so generated by the modulating signal generator 72 that thefrequency of the ultrasounds after the lapse of a certain period of time(T=10 μS) be 4f₀ and their wavelength, λ₀/4. Repetition of such actionscauses the therapeutic ultrasounds emitted from the therapeutictransducers 50 to be modulated in frequency in the direction of the timeaxis.

In this embodiment, even if, for example, the reflected wave and theincident wave overlap each other within the skull, the overlappingreflected wave and incident wave will differ in frequency. Since theinterference pattern between the reflected wave and the incident wavetherefore is not fixed, the intensity of the interference wave generatedby the interference between the reflected wave and the incident wave canbe restrained.

To add, whereas the timing of modulating the frequency can be set asappropriate, in this embodiment the frequency of therapeutic ultrasoundsis modulated every time an emitted ultrasound is transmitted from thebrain surface into the skull and proceeds into the brain (e.g. 10 μS) sothat the inference pattern of the therapeutic ultrasounds may not befixed at all. The point is that the frequency should be modulated in thedirection of the time axis on the basis of the basic waveforms.

Incidentally, the modulation value of the frequency can be set asappropriate. For example, if the frequency is so modulated that thereflected wave and the incident wave deviated from each other by ¼ to ½wavelength, the reflected wave and the incident wave will so interfereas to cancel each other. Therefore, the intensity of the interferencewave can be further prevented from increasing.

Although this embodiment has been described with the use of theultrasound probe 10 of the first embodiment, the ultrasound apparatus ofthis embodiment can also be applied where the diagnostic probe and thetherapeutic probe are separated from each other.

An eighth embodiment to which an ultrasound probe and an ultrasoundapparatus according to the invention are applied will be described withreference to FIGS. 12 and 13. This embodiment differs from the seventhembodiment in that the incident direction of therapeutic ultrasounds isshifted at every set time. FIG. 13 is a diagram for describing theprinciple of avoiding interference between the incident wave and thereflected wave.

Thus, when driving signals are generated by the therapeutic ultrasoundtransmitting device 24 of FIG. 12, preset delay data are assigned to thephase shifter circuits 74 a through 74 m at every set time (e.g. 0.1second). As this causes the ultrasounds emitted from the therapeutictransducers 50 to be deflected, the emitting direction of the ultrasoundbeam is altered. The angle (θ) of altering the ultrasound beam may bechanged as appropriate.

In this embodiment, as shown in FIG. 13, the proceeding direction of theincident wave and that of the reflected wave of the therapeuticultrasounds are no longer on the same straight line. Thus, since theincident wave and the reflected wave become different in direction,interference between the incident wave and the reflected wave can beavoided.

Further, although the set time for altering the emitting direction ofultrasounds is supposed to be 0.1 second in this embodiment, it can beset as appropriate. For example, if the incident wave and the reflectedwave overlap and interfere with each other, the interference wave maygenerate cavitations (bubbles) in the blood vessel. The generatedcavitations, after growing in size gradually, are ruptured. The impactof the cavitations may bring on a side effect on the living tissue. Itis therefore desirable to alter the emitting direction of ultrasoundsbefore cavitations arise.

Although this embodiment has been described with the use of theultrasound probe 10 of the first embodiment, the ultrasound apparatus ofthis embodiment can also be applied where the diagnostic probe and thetherapeutic probe are separated from each other.

Although the present invention has been hitherto described withreference to the first through eighth embodiments thereof, the inventionis not limited to them. For example, besides cases of treating cerebralinfarction, the ultrasound probe and the ultrasound apparatus accordingto the invention can also be applied to therapy of myocardialinfarction. When treading myocardial infarction, the ultrasound probe iskept in contact with the chest, and diagnostic and therapeuticultrasounds are emitted toward the thrombosis formed in the coronaryartery through gaps between chest ribs.

The ultrasound probe and the ultrasound apparatus according to theinvention can be applied not only to dissolving thromboses but also todissolving abnormal solids formed within the body of inorganicsubstances or salts (e.g. calculi).

The ultrasound probe and the ultrasound apparatus according to theinvention can also be used for cerebral infarctions of various types.Cerebral infarctions, for example, include lacunar infarction,atherothrombotic infarction and cardiogenic cerebral embolism. Lacunarinfarction is a small infarcted focus formed in a deep part of the brainby the twining of a thin cerebral artery due to damage by high bloodpressure. Atherothrombotic infarction occurs when the sclerosis of acarotid artery or a relatively thick artery within the skull(atherosclerosis) narrows that artery, inviting the formation of athrombosis in that position to block the blood stream. Cardiogeniccerebral embolism is a blockade of the blood stream by a lump of blood(thrombosis) formed in the heart, peeled off and flowing into a cerebralartery. Whereas the thrombosis in the infarcted region should bedissolved in a short period from the time when a cerebral infarction hasoccurred in any of these types of cerebral infarction, the ultrasoundprobe and the ultrasound apparatus according to the invention canpromptly and readily dissolve the thrombosis.

INDUSTRIAL APPLICABILITY

As hitherto described, the present invention makes it possible torealize an ultrasound probe and an ultrasound apparatus well suited toultrasound therapy.

1. An ultrasound probe, comprising: a plurality of therapeutictransducers arrayed in a longitudinal direction of the ultrasound probe,for emitting therapeutic ultrasounds to a subject; a plurality ofdiagnostic transducers arrayed in a longitudinal direction of theultrasound probe, for emitting diagnostic ultrasounds to the subject andreceiving the diagnostic ultrasounds reflected by the subject; and soundinsulators between the plurality of therapeutic transducers, wherein: astacking structure is provided where at least one of the diagnostictransducers is stacked over the top of one of the ultrasound emittingfaces of the therapeutic transducers and over one of the soundinsulators, and at least two of the diagnostic transducers are stackedover the ultrasound emitting face of the therapeutic transducers.
 2. Theultrasound probe according to claim 1, wherein the ratio between thearray pitch of the plurality of therapeutic transducers and the arraypitch of the plurality of diagnostic transducers is not an integralratio.
 3. The ultrasound probe according to claim 1, further comprisinga backing material having a thickness of half the wavelength of thetherapeutic ultrasounds and disposed superposing over the reverse facesof the therapeutic transducers to the ultrasound emitting faces thereof.4. The ultrasound probe according to claim 1, further comprising acooling device or devices joined to at least either of the therapeutictransducers and the diagnostic transducers.
 5. The ultrasound probeaccording to claim 4, wherein the cooling device or devices cover atleast one of: a reverse face to the ultrasound emitting face of at leasteither of the therapeutic transducers and the diagnostic transducers;and a side face of at least either of the therapeutic transducers andthe diagnostic transducers.
 6. The ultrasound probe according to claim4, further comprising a metallic foil in contact with the cooling deviceor devices over the ultrasound emitting face of at least either of thetherapeutic transducers and the diagnostic transducers.
 7. Theultrasound probe according to claim 1, wherein an ultrasound aperture Dof the ultrasound probe is computed by:D=N×p ₂ where N is the number of therapeutic transducers and p₂, thearray pitch of the plurality of diagnostic transducers.
 8. An ultrasoundapparatus, comprising: an ultrasound probe according to claim 1; atherapeutic transmitting device for generating driving signals for thetherapeutic transducers; a diagnostic transmitting device for generatingdriving signals for the diagnostic transducers; an image constructingdevice for reconstructing ultrasound images on the basis of reflectedecho signals received by the diagnostic transducers; and a detectingmeans for detecting the state of the therapy of the subject with thetherapeutic ultrasounds, wherein the therapeutic transmitting device hasa warning function to output warning information on the basis of thestate of the therapy detected by the detecting means.
 9. The ultrasoundapparatus according to claim 8, wherein the therapeutic transmittingdevice controls driving signals for the therapeutic transducers on thebasis of the state detected by the detecting means.
 10. The ultrasoundapparatus according to claim 8, wherein the detecting means detects atemperature correlated to at least either of the therapeutic transducersand the diagnostic transducers and, when the detected temperaturesurpasses a setpoint, outputs the detected temperature to thetherapeutic transmitting device.
 11. The ultrasound apparatus accordingto claim 8, wherein the detecting means figures out the blood streamsignal from the Doppler shift of reflected echo signals and, when thedetected blood stream signal surpasses a setpoint, outputs the bloodstream signal to the therapeutic transmitting device.
 12. The ultrasoundapparatus according to claim 11, further comprising an injection controldevice for controlling the dose of a thrombolytic agent to be injectedinto the subject, wherein the injection control device controls theinjected dose of the thrombolytic agent on the basis of the blood streamsignal detected by the detecting means.
 13. The ultrasound apparatusaccording to claim 8, wherein the therapeutic transmitting device sogenerates driving signals for the therapeutic transducers as to preventinterference between a reflected wave reflected by a region in thesubject and an incident wave brought to incidence into the subject fromthe therapeutic transducers.
 14. The ultrasound apparatus according toclaim 13, wherein the therapeutic transmitting device generates thedriving signals of either a pulse wave or a burst wave from a basicwaveform by controlling the duration of emission and the duration ofrest.
 15. The ultrasound apparatus according to claim 13, wherein thetherapeutic transmitting device generates the driving signals forultrasounds resulting from modulation of frequencies in the direction ofthe time axis on the basis of the basic waveform.
 16. The ultrasoundapparatus according to claim 13, wherein the therapeutic transmittingdevice so generates the driving signals as to differentiate the emittingdirection of ultrasound beams emitted from the therapeutic transducersfrom the direction of the reflected wave reflected by a region in thesubject.